As a conventional magnetic core material for the reactor, a stacked electromagnetic steel plate or a soft magnetic metal power core can be used. Although the stacked electromagnetic steel plate has a high saturation magnetic flux density, it has a problem of that if the driving frequency in the circuit of the power supply exceeds 10 kHz, the iron loss will become greater and will cause a decreased efficiency. The soft magnetic metal powder core is widely used as the driving frequency becomes higher because its iron loss at a high frequency is less than that of the stacked electromagnetic steel plate. However, the iron loss of the soft magnetic metal powder core may not low enough, and some problems are there such as the saturation magnetic flux density is inferior to that of the electromagnetic steel plate.
On the other hand, the ferrite core is well known as a magnetic core material with a small iron loss at a high frequency. However, the ferrite core has a lower saturation magnetic flux density compared to the stacked electromagnetic steel plate or the soft magnetic metal powder core, thus a design is needed to provide a relatively large section in the magnetic core so as to avoid the magnetic saturation when a large current is applied. In this respect, a problem rises that the shape becomes larger.
In Patent Document 1, a reactor has been disclosed in which a composite magnetic core is used as the magnetic core material so that the loss, size and the weight of the core are reduced, wherein the composite magnetic core is obtained by combining a soft magnetic metal powder core used in the portion for winding the coil and a ferrite core used in the yoke portion.